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Tuesday - August 26, 2008

From: Grafton, MA
Region: Northeast
Topic: Diseases and Disorders
Title: Strange growth on oak tree
Answered by: Nan Hampton


i have a very strange round segmented growth on a tree in my yard. i think the tree is a chinkapin oak and the growth is a reddish color. it looks like a ball with suction cups on it. it is very strange looking thing and I have not been able to id it anywhere!


It sounds as if your tree has a gall.  This is a growth that the tree makes in response to an insect or another organism such as a mite or a fungus.  Many galls are caused by an insect laying its eggs in the tree.  The insect hatches inside the gall growth, feeds on the growth and then emerges from the gall to continue its life cycle.  Here is more information about oak galls from the University of Kentucky and here is a Gallery of Common Galls from North Carolina State University.  Your growth sounds a bit like a horned oak gall.  If you don't find your growth in one of these links, please send us a photo and we will do our best to identify it.  Please visit the Ask Mr. Smarty Plants Plant Identification page to read instructions for submitting photos.

Note from Mr. SP:  After this answer was posted, someone else sent us a photograph that sounds very much like the gall described above.  We submitted the photo to BugGuide.net and asked if anyone could identify it.  Someone did identify it as being made by a gall wasp, Adleria quercusstrobilana, in the (Family Cynipidae), laying its eggs in the stem of the tree.


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